This technique is intended to compensate for a transient response at the ADC input when the ADC switches between acquisition and conversion modes. Some components will require this capacitor in order to function properly typical sizes are 1-10 uF or higher.Įxample capacitor selection for the analog and digital voltage rails on an ADC. This is as simple as putting a capacitor at the VREF pin by the ADC. The idea with this capacitor is to provide compensation for any variation in the potential between the VREF rail and the system’s analog ground pin. The typical filter for an ADC voltage reference is a simple low-ESR capacitor (ceramic chip capacitor). In either case, filtering may be needed to ensure low-noise signal acquisition. This precision reference can have its own output noise, or the routing between the reference and the ADC’s VREF pin could pick up noise from some other source. The three primary areas where a circuit designer may need to reduce noise in an ADC are:Īll ADCs need a precision reference voltage source that will be used as a comparison to the signal level and will determine the level of quantization. Pay attention to these points Types of ADC Filters Different types of ADC filter circuits should be applied in different situations, and not all ADCs will need to include every possible filtration circuit to operate properly. In this article, we’ll examine the design steps involved in building ADC filter circuits to target noise in three areas. Designing ADC filter circuits is rather simple when viewed from the signal perspective, but care should be taken when filtering a reference or input charge compensation. In all of these instances, an ADC filter circuit might be needed to ensure highly precise signal acquisition. Let’s set the scene: you have an ADC, but it has some phantom noise problems due to some issue on the signal itself, due to the stability of the reference, or due to the internal operation of the ADC in the presence of excess charge.
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